1. Field of Disclosure
The present disclosure of invention relates to a method of driving a display panel and a display apparatus structured for performing the method. More specifically, the disclosure relates to pre-charging of an LCD panel operating with a column inversion structure.
2. Description of Related Technology
Generally, a liquid crystal display (LCD) apparatus includes a first substrate including pixel or subpixel units each having a respective, to-be-charged pixel electrode, a second substrate including a common electrode and a liquid crystal layer disposed between the first and second substrates. An electric field is generated by voltages developed between the to-be-charged pixel electrode and its counterfacing portion of the common electrode. By adjusting an intensity of the electric field, transmittance of light passing through the liquid crystal layer may be adjusted so that a desired image may be formed and displayed.
If an electric field having a constantly same direction or polarity is continuously applied to the liquid crystal layer, a desired characteristic of a liquid crystal may be degraded. In order to prevent the degradation of the characteristic of the liquid crystal, an inversion driving method is used which repeatedly inverts a phase of a data voltage applied across the liquid crystal where the phase is with respect to a common voltage applied to the common electrode. One of various inversion driving methods is a dot inversion method (DIM) in which data drive phases of adjacent subpixels or dots across the entire display frame are alternated and reversed repeatedly such as in each successive display frame. This legacy DIM approach creates a checkerboard pattern of plus (+) and minus (−) polarities in each frame as across the matrix of subpixels provided on the display area.
When employing the DIM, the degradation of the characteristic of the liquid crystal may be prevented or reduced, however, the process of providing the inverted or not inverted data voltages to respective individual pixels may be complicated. Additionally, signals on the data lines may be delayed as a result, and power consumption of the LCD apparatus may be disadvantageously increased. In order to solve the above-mentioned problems, a data column inversion method has been proposed in which image data voltages having polarities different from each other are applied to adjacent data lines of the display substrate. When employing the column inversion method, the polarity of data voltage applied to each respective data line is inverted in each successive frame so that the applying process of the data voltage may be simplified, and the delay time of the signals on the data lines may be decreased. To obtain the DIM checkerboard effect while instead using the column inversion method, subpixels in a single column are alternately connected to one of two data lines adjacent to the column of subpixels where one data line is driven under a first polarity at the time (e.g., positive (+)) and the other data line is driven under an opposed second polarity at the time (e.g., negative (−)). Accordingly, the checkerboard pattern of positives (+) and negatives (−) may be obtained even though each data line is being driven under just one polarity scheme in the given frame.
In addition, in recent times it has become desirable to provide high resolution in the LCD apparatus so that an image having high display quality may be displayed. As the resolution of the LCD is increased, time to charge each subpixel tends to become shortened.
To compensate for the shortened charging time, a precharge driving method is generally used. In the precharge driving method, a precharge voltage that is assumed to be approximating the magnitude which next is to be applied to the pixel electrode is pre-charged onto the pixel electrode. Thus, although the charging time is shortened in high resolution LCD devices, the desired final data voltage may be sufficiently charged onto the pixel electrode if that electrode has been appropriately pre-charged to a magnitude close to the final one.
However, when a conventional precharge driving method is used in combination with certain variations of the DIM-checkerboard mimicking, column inversion method, the appropriate precharging voltage is sufficiently charged only onto some pixel electrodes but not onto other pixel electrodes (where precharging is based on a previous data voltage applied to nearby pixel electrodes). Because some pixels receive an appropriate pre-charge and some do not, a difference of effective pre-charging relative to desired luminance can develop as between two adjacent rows of pixels. Accordingly, a difference of actual luminance between two adjacent rows of pixels (as opposed to desired luminances) may be undesirably created due to the difference of effective or ineffective pre-chargings applied to those adjacent rows. Thus, a horizontal dark or bright streak line may appear to be displayed on a display panel as an undesirable artifact resulting from the pre-charging process so that displayed image appears to have defects.